An engine performs an exhaust gas recirculation (EGR) which recirculates exhaust gas back to an intake side in order to reduce nitrogen oxide in the exhaust gas, and sufficient EGR gas supply should be available for smooth EGR operation.
Further, during cold starting of the engine, a catalyst of a catalytic converter, which purifies a harmful material in the exhaust gas, should be able to quickly reach a LOT (Light Off Temperature). To this end, the exhaust gas energy should be able to be delivered to the catalyst as much as possible.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.